Heat exchanger

ABSTRACT

The present disclosure relates to a heat exchanger that is characterized by including at least one collector and at least one tube, in which case the tube is installed in the collector by at least one seal disposed between the collector and the tube in such a manner that fluid connection is possible between the collector and the tube, wherein the tube includes at least one reinforcing element. The present disclosure also relates to a method of installing a heat exchanger and a method of manufacturing a heat exchanger, in which case at least one tube is installed in at least one collector by at least one seal disposed between the collector and the tube in such a manner that fluid connection is possible between the collector and the tube, wherein at least one reinforcing element is provided in or to the at least one tube.

TECHNICAL FIELD

The present disclosure relates to a heat exchanger and a method of manufacturing and assembling the same, and more particularly, the heat exchanger according to the present disclosure is associated with an air flow heat exchanger that is assembled by mechanical assembly (MA) as well as controlled atmospheric brazing (CAB).

BACKGROUND ART

In general, a vehicle is equipped with an engine cooling system that includes a heat exchanger, also typically referred to as a cooler. During engine operation, heat is transferred from an engine to coolant flowing through the engine. The coolant then flows from the engine to the heat exchanger through a plurality of lines of the heat exchanger in which heat is released from the coolant to cooling air flowing from the outside. This process is continuously repeated and simultaneously cools the engine.

The heat exchanger is also inserted into intercoolers of a turbocharger and a compressor, and is inserted to further cool parts for supply of power in an electric vehicle.

The heat exchanger commonly includes a plurality of parallel tubes, which form a heat exchange section, also referred to as a matrix, the ends of which are each connected to a chamber called a collector. Liquid coolant flows through an inlet into one of the collectors, and then flows through the parallel tubes to another collector from which the coolant is discharged through an outlet. In this case, the flow of air flowing between the tubes acts to conduct the heat of the coolant. In order to increase the surface area of the matrix and the thermal conductivity of this matrix surface area, the tubes are typically connected through a plurality of ribs, which extend parallel to each other and perpendicularly to the tubes or extend in a zigzag manner.

While the collectors may be partly or wholly made of plastic material, the matrix of the heat exchanger is made of metal, for example, an aluminum alloy. The collector has a substrate which is also typically made of metal, and the tubes are connected to the end of the substrate. The sidewalls of the collector may be made of metal, but these collector sidewalls are often made of plastic material for reason of cost, where the plastic material is fixed to the metal substrate, for example, through metal beading. In this case, a seal, for example a flexible compressible ring seal, is also provided, which extends around the connection position between the substrate and the sidewalls of the collector and provides sealing required for a low-pressure coolant circulation system.

Two methods are known in connection with manufacturing the heat exchanger as described above. The first method involves the use of high-temperature hard soldering based on the flux of the controlled atmospheric brazing (CAB), to connect the metal tube of the matrix to the metal portion (substrate) of the collector. The CAB described above is hereinafter referred to as a “heat treatment and bonding method”.

The other known method for manufacturing the above heat exchanger involves the use of mechanical assembly (MA) for mechanically assembling the matrix and the collectors, instead of welding or brazing adjacent metal parts. In this specification, the connections produced in the above manner without welding or brazing processes are expressed as “mechanical connections” or “mechanically connected”. At the same time, the adjacent parts are mechanically coupled by separate contact parts that are not interconnected in a different manner.

In the CAB process, metal flat tubes are spaced apart from each other by metal ribs extending generally in a zigzag pattern across the gap between the tubes. In a plurality of CAB heat exchangers, each of tubes includes individual channels, or alternatively, individual channels that are arranged in pairs side by side, which are separated by separation walls extending longitudinally to form a dual channel. The tubes are generally narrow and elongated, i.e., basically rectangular when viewed in cross-section, and basically include two flat sides facing each other and two short curved sides or side ends. The ribs are soldered on the long sides and do not extend over the boundary region of the short sides. The respective tube ends are inserted into the through-holes in the metal substrates of the collectors, in which case the gap size of the adjacent metal parts is maintained at about 0.15 mm, in turn the gap may be sealed by a soldering paste, and soldering connection is made between parts, namely between the tube and the collector substrate, while passing through soldering ovens. To provide high thermal conductivity, the metal parts are preferably made of an aluminum alloy.

In the MA process, collectors as well as ribs and tubes are coupled through forced bonding or mechanical connection. The ribs always extends at right angle to the tubes, instead of being folded or waved as in the CAB process, so that they extend along the tubes and therefore have openings through which the tubes pass. In this arrangement, the ribs are closely adjacent and arranged in parallel and typically extend between the front and back sides of the matrix. The tubes have a circular cross-section and first have a diameter smaller than the diameter of the rib openings into which the tubes are inserted. To provide high thermal conductivity, all metal parts are preferably made of an aluminum alloy. A tool, also referred to as a “projectile”, namely the diameter of the tool is greater than the initial inner diameter of the tube, is moved into all tubes to expand the tube and press it into the openings in the ribs. The ribs are thus fixed to the tube by mechanical connection. The substrate of each collector also has openings for the tube end, in which case the openings are made such that there is sufficient space for the plastic or rubber sealing elements inserted between the metal material and the substrate. In this case, many methods for sealing a seal are known, for example the use of conical tools pressed against tube ends is known, thereby mechanically expanding the tube ends with the consequence that the seal may be compressed.

Each method has certain advantages and disadvantages over other methods. Accordingly, the heat exchangers assembled by the CAB method are mechanically more robust, not only due to providing relatively higher heat transfer performance at a given heat exchanger size, but also due to the used flat tube extending between the front and back sides of the heat exchanger, which is because the ribs are protected. Of course, there are drawbacks to be noted, that is, the soldering process requires a long processing time through expensive soldering ovens. Furthermore, the cooler tube experiences thermal alternating stresses (increase and decrease in temperature of heat exchanger parts) during operation of the engine and the cooling system, which leads to a load because adjacent tubes may extend differently and the axial load may be applied to a tube given by the adjacent tubes.

That is, in order to increase heat transfer power, the tubes are arranged side by side such that the surface areas of the adjacent tubes face each other and, between these tubes, a space for the ribs through which the cool air coming from the outside may flow is defined. The structure of the above tubes is preferred only if these tubes form a relatively large surface area, in which case the cool air may pass through the surface area without unduly interfering with the course of the air flow through the heat exchanger. On the other hand, however, the above type of collector/tube junction is susceptible to failure along the collector/tube connection, especially around the tube end and where the tube walls are significantly curved due to stress concentration, which is because the thermal expansion of the heat exchanger is commonly not constant during operation, and consequently cracks leading to premature failure and leakage of the heat exchanger may occur depending on the flow pattern of coolant at certain portions of the heat exchanger.

The MA method may be used to manufacture less expensive heat exchangers because it prevents the use of costly soldering ovens. Since the mechanical connection process is used between the tube ends and the collectors, the press connection process may be designed to allow the certain longitudinal movement of the tubes and collectors caused due to different thermal expansions during heating or cooling of the heat exchanger. The fully mechanically assembled heat exchanger basically reduces or (on this account) removes the thermal stress between heat exchanger parts, resulting in an increase in reliability and service life of the heat exchanger. However, since such heat exchangers are less efficient during heat transfer at a given size, the resulting mechanically connected heat exchangers must be larger in size to provide the heat transfer power as the given sized CAB heat exchanger. In addition, in the case of the MA heat exchangers having a relatively large size as described above, more space must be provided.

Furthermore, in the heat exchanger assembled by the MA, the ribs extending parallel to each other from the front to the back of the circular cooler tubes are also less robust as in the ribs of the heat exchanger, made by the CAB, built between the flat tubes in a zigzag manner. That is, in this case, to maximize heat transfer power, the ribs must be thin in thickness, about 0.1 mm: but these ribs are easily deformed also by finger pressure. Each of these damages reduces the flow of cool air through the heat exchanger, and in a vehicle cooler, this cumulative damage also reduces matrix cooling power since stones or debris may strike the cooler.

In order to utilize the advantages of the above-mentioned two methods, German Patent DE 10 2015 113 905 A1 has proposed a method for soldering tubes and ribs, subsequently inserting tube ends into the through-holes of collectors, and then mechanically connecting them to a collector substrate while interposing a seal therebetween. Of course,—especially when using flat tubes with excellent heat exchange efficiency—, the tube walls become soft after the soldering process to be, on the one hand, easily bent, which may damage the rib structure, and on the other hand, there is a tendency to teardown in the tube end deformation assembly step, i.e., compared to an MA cooler with a relatively thicker tube wall, the mechanical connection with the collector is very difficult, for example, due to enlargement of the tube end.

DISCLOSURE Technical Problem

An object of the present disclosure is to provide a heat exchanger and a method of manufacturing and assembling the same for producing a very stable heat exchanger.

Technical Solution

The above object is accomplished by a heat exchanger having the features defined in claim 1 and a method of manufacturing a heat exchanger having the features defined in claim 8. Preferred improvements are set forth in the dependent claims.

Accordingly, at least one tube includes at least one reinforcing element. It has been found that such a reinforcing element significantly increases the stability of the tube. As a result, the tube can withstand much of the pressure transmitted to the tube through the seal disposed between the tube and the collector. Particularly, after soldering, the material of the tube, typically an aluminum alloy, is relatively soft and may be easily bent/flexible or crack when a load is applied thereto. Thus, according to the present disclosure, the tubes are preferably deformed before soldering and/or after inserted into the collector according to an embodiment, wherein such deformation forms the reinforcing elements according to the present disclosure. Optionally, the tube position in the collector can be fixed at the same time in this context.

In the first experiment, the heat exchanger according to the present disclosure has been found to have significantly improved thermal shock resistance. The above result is, on the one hand, due to the possibility that the tube is made, for example, by the seal between the tube and the collector, which is expanded or contracted by a variation in temperature.

In this context, it should be emphasized that liquid coolant may also flow through the tubes of the heat exchanger according to the present disclosure, so that the coolant may be cooled by the air circulating in the tubes. However, the heat exchanger according to the present disclosure may also be used to cool, for example, gaseous media such as air that may flow through the tubes. As will be described in more detail below, the reinforcing element provided in at least one tube, preferably in the entire tube, may be provided, for example, in a wide variety of embodiments, such as one or more grooves or separation walls within the tube, wherein the one or more grooves or separation walls basically extend, perpendicular to the relatively long axis of the tube designed to be flat when viewed in cross-section, either as an insert or as a tube end upper attachment (provided from the outside). Ultimately, the wall of the tube may be bent to basically extend perpendicular to the tube axis.

Preferred improvements of the heat exchanger according to the present disclosure are set forth in the further claims.

Preferably, the reinforcing element is provided, i.e., in the range of only a few millimeters or centimeters, especially on the side of the tube not the collector, for example, in front of and/or behind the connection position between the tube and the collector in the axial direction of the tube. In certain applications, the reinforcing element is provided only at the end of the tube. In connection with the material thicknesses of the reinforcing element which is described above and will be described below, the range of 0.2 mm to 1.0 mm is preferable. In connection with the length in the axial direction, suitable characteristics are expected in the dimension of 2 mm to 15 mm.

Advantages of the present disclosure are exhibited in the tubes designed to be flat especially when viewed in cross-section, so that the above tubes designed to be flat have a long axis and a short axis when viewed in cross-section. In particular, the present disclosure makes it possible to connect the flat tube having a long axis of 12 mm or more to the collector, especially without concern for tube deformation which is problematic in the axial direction in which its length is short when the pressure is applied to the side of the seal during operation. Alternatively or additionally, particularly to realize an efficient heat exchanger, it is preferable that the long axis has a length of up to 100 mm.

As already illustrated above, the stabilization according to the present disclosure can be achieved particularly effectively by at least one inner rib that basically extends perpendicular to the long axis. Ultimately, the wall of the tube, in particular the wall extending parallel to the relatively long axis, can be stabilized by the wall basically extending perpendicular to the tube axis, especially bending in the vertical direction.

At the same time, according to the present disclosure, the stabilization in the tube can be provided by designing at least one reinforcing element, in particular, as an insert disposed in the connection region for the above-mentioned collector. Preferably, the insert is connected at least locally to the inner wall of the tube, for example by soldering, preferably by soldering which may be carried out during the soldering of the tube and the collector. The dimension of the above inserts basically corresponds to the dimension of the deformed tube ends, as will be described in more detail below, with the consequence that the inserts can be inserted easily.

In connection with the effective form of the insert for supporting and reinforcing the tube in the region as large as possible from the inside, it has been found that it is desirable for the insert to have at least one step and/or at least one web. Alternatively or additionally, it may also be contemplated that the insert has an elliptical or circular shape.

While the above-mentioned inserts are implemented from the inner side, the at least one reinforcing element may also be formed as a collar or upper attachment provided on the tube end from the outside. The above type of collar may have an inner cross-section that can receive the tube end along the longitudinal axis of the tube in the first region, and may have an inner cross-section that is reduced in the second region outside the tube but provides a flow cross-section in the tube end region. The above collar may be connected to the tube end as described previously in connection with the insert, in which case the collar is soldered to the collector and the tube is soldered to the collar. The inner cross-section of the above collar basically coincides with the outer cross-section of the tube, with the consequence that the collar can be installed in the tube in a simple manner.

In general, it is now desirable to solder at least one reinforcing element to the tube, which enables efficient manufacturing by allowing the soldering of the tube and collector to be carried out in a single working process.

It should be emphasized that the above-mentioned object of the present disclosure is also accomplished by the method described in claim 8, wherein all the features and details specified in relation to the heat exchanger described above and below may be applied to the method according to the disclosure and it may be applied in reverse. In addition, the entire details of the foregoing description relating to the related art may be applied to the heat exchanger as well as to the method of manufacturing a heat exchanger.

Accordingly, in certain applications, it may be desirable to integrally form at least one inner rib as a reinforcing element, particularly with the tube in a built-in manner.

Although the foregoing illustrates that the tube and the at least one reinforcing element are soldered during the soldering of the tube and the collector, such soldering may be performed before or after the described steps. In this context, it should be noted that the tube is traditionally (if absolute) soldered only at one side thereof to the collector. In other words, the tube is fixed on at least one side of the collector by the seal disposed therebetween, and the elasticity of such a seal is utilized during installation. In addition, the one or more reinforcing elements may be soldered to the tube, the ribs, the fins, or the spaces disposed between the tubes, together with tube soldering.

In connection with manufacturing at least one reinforcing element, it is currently preferred to manufacture the reinforcing element by extrusion molding, for example when it is an insert, and/or to manufacture the reinforcing element by bending, for example when it is a wall of the tube. The described collar may be bent after extrusion molding.

Advantageous Effects

As at least one tube of the present disclosure has at least one reinforcing element, it is possible to significantly increase the stability of the tube.

Thus, the tube can withstand much of the pressure transmitted to the tube through the seal disposed between the tube and the collector.

The present disclosure is not limited to the above effects, and it should be understood that the disclosure includes all effects which can be inferred from the detailed description of the disclosure or the configuration of the disclosure defined by the appended claims.

DESCRIPTION OF DRAWINGS

Subsequently, the present disclosure will be described in more detail with reference to the embodiments illustrated in the drawings, in which:

FIG. 1 is a perspective view illustrating main parts of a heat exchanger according to the present disclosure; and

FIGS. 2 to 10 each illustrate a tube end of the heat exchanger according to the present disclosure with a preferred embodiment of a reinforcing element according to the present disclosure.

BEST MODE

FIG. 1 illustrates main elements of a heat exchanger 10 according to the present disclosure, together with a plurality of flat tubes 12 when viewed in cross-section and two substrates 14 of collectors arranged at the ends of these tubes. As can be seen in FIG. 1, the flat tubes 12 are traditionally aligned horizontally and in parallel to each other in a mounted state, and to improve the heat conduction of the tubes, ribs or pins 16, for example in the form of waves, may be provided between the tubes 12. In connection with the drawings, it should be particularly noted that application is illustrated in which heat is transferred from charge air to ambient air in FIGS. 1, 8, 9, and 10. In other words, ambient air is used to cool the charge air in a charge air cooler. On the other hand, FIGS. 2 to 7 illustrate tubes in radiator application in which heat is transferred between liquid coolant and ambient air.

In response to the cross-sectional configuration of the tubes, each of the substrates 14 has openings into which the tube ends are inserted, in which case each section of a seal is disposed between the tube end and the substrate 14 of the collector. The shape of this seal basically corresponds to the shape of the substrate, i.e., the seal has openings corresponding to the openings in the substrate 14 for insertion of the tube 12. In this case, the seal is traditionally extends in a tube direction as well as being flat, and has a web, an edge or a collar surrounding its periphery, where the web, the edge or the collar extends along the circumference of the individual opening in the substrate 14 so that a sealing material is disposed between the tube and the opening in the substrate 14 traditionally in such a manner as to surround the outer surface of the tube. The seal may be inserted into the substrate from the side of the collector as illustrated on the right of FIG. 1, namely from the right in FIG. 1, or from the side of the tube. The seal is traditionally made of an elastic material, especially a rubber material, and thus preferably allows for certain deformation and extension of the tubes mounted in the substrate. Since the above deformation may lead to a load which may cause crack formation at the tube ends, reinforcing elements may be provided according to the present disclosure, which are already illustrated in various embodiments on the right of FIG. 1 and will be described in detail below.

For example, FIG. 2 illustrates an embodiment in which the end region of the tube is reinforced by an insert 18, in which case the insert has a flat cross-section basically corresponding to the inner cross-section of the tube 12. In connection with the embodiment of FIGS. 2 to 7, it should be contemplated that the tube basically has a first cross-section that is relatively small in size over most of its longitudinal extension, in other words, between the two substrates 14 according to FIG. 1, and has a second cross-section that is relatively large in size in its end region. To mount the tube in the substrate 14, the second region that is relatively large in size as described above is inserted into the individual opening in the substrate and then soldered, for example, with the opening. The inserts illustrated in FIGS. 2 to 6 are typically provided at the end of the region having a large cross-section, so that the inserts can provide stability required in this case.

The shape of the above-mentioned tube having a relatively large cross-sectional region and a relatively small cross-sectional region may result in deformation, and the individual insert may be subsequently inserted, in which case the position of the insert is defined between the relatively large cross-sectional region and the relatively small cross-sectional region by steps (such as the rail of the ladder). In other words, the tube ends are deformed in such a manner that the cross-section of the tube end is higher in height and narrow in width in a first step, for example, as illustrated in FIGS. 2 to 4. In other words, the cross-section is deformed into an “elliptical” shape, but it may also have an undeformed cross-sectional region in this case. After the deformation process described above, the inserts may be inserted into the deformed end and then soldered to the tube. In this regard, the outermost end of the tube may be slightly closed through section formation in which the section is gradually tapered, for example, as can be seen in an observer direction of viewing the drawings in FIGS. 2 to 4, to fix the inserted insert in place.

In connection with the insert 18 illustrated in FIG. 2, it should be contemplated that the insert basically has a flat rectangular cross-section with a long parallel side and a short rounded side and, in the case illustrated, two webs 20 that are perpendicular to the long side. Particularly, the webs enable stability to be provided in an axial direction in which the length of the cross-section that is flat from top to down in FIG. 2 is short.

This applies equally to the insert 18 illustrated in FIG. 3 basically having the same cross-section as the cross-section of FIG. 2, but the insert illustrated in FIG. 3 has only one web which is given through quadruple bending. The insert starts from the upper surface thereof to be first bent in an S-shape, resulting in a first end 22 extending in a manner that is parallel to the long side and abuts on the upper boundary of the insert 18. To form the web 20, the substantially central region of the long side is basically provided with an additional bending of about 90°, in which case the web is supported at its lower region on the lower surface of the insert by the additional bending.

In addition, the embodiment of FIG. 4 is similar to the left half of the insert 18 in the formation according to FIG. 3 in that the web 20.1 is basically formed at a position corresponding to approximately one-third along the length of the long side (from left to right in FIG. 4). For the formation of an additional web 20.2, the insert is bent upward in an S-shape again from the lower end in such a manner that the end 24 abuts on the upper surface of the insert. In this case, the two webs 20.1 and 20.2 enable very excellent stability to be provided almost corresponding to the embodiment of FIG. 2.

This applies equally to an embodiment of FIG. 5 having an elliptical insert 18 in a substantially central region in the tube along the long side of the tube cross-section, wherein the insert has a long axis which occupies about 40% to 60% of the long axis of the tube cross-section. FIG. 5 further illustrates a section of a collector substrate 14 and a seal 26 disposed between the tube end of the substrate.

The elliptical insert 18 illustrated in FIG. 5 may have a circular cross-section as illustrated in the embodiment of FIG. 6, where the side ends of the tube in the embodiment of FIG. 6 are provided with circular inserts 18. The diameter of each circular insert corresponds to about one-third of the length of the long axis in the tube cross-section in the case illustrated.

While the embodiments described so far have the inserts inserted into the tube, FIG. 7 illustrates an embodiment in which reinforcement is made by the section of a tube itself, on the one hand, and by the type of a collar 28, on the other hand. The shape of the collar corresponds to the tube end according to the embodiments of FIGS. 2 to 6 and has a first relatively large cross-section facing the observer in FIG. 7, wherein the cross-section may receive the tube end. To the first cross-section, a relatively small cross-section that is away from the observer and faces the collector in the mounted state in FIG. 7 is connected, and at the same time, this cross-section provides a step basically surrounding its periphery between two sections of different cross-sections, and this step determines the location of the tube when installing the tube in the collector. In the embodiment of FIG. 7, on the one hand, the collar 28 may act as a reinforcing element. In FIG. 7, however, an additional measure is illustrated in which two inner ribs 30 are formed in the tube, integrally with the walls of the tube, where these ribs basically extend in an axial direction in which the length of the tube cross-section is short. As can be seen in FIG. 7, the expression “basically” means a deviation of up to 10° from the direction mentioned in this case. In the example illustrated, the ends of the ribs are bent again by about 90° or more to provide a circular round support on the upper inner wall of the tube. In this regard, the advantages of the installation of the collar as a reinforcing element are that a groove and/or a possible gap at the position where the ribs 30 bent from the individual tube wall collide when the collar is soldered to the tube end is closed by soldering.

FIG. 8 illustrates an embodiment similar to that of FIG. 6, but in this case the summed diameter of the plurality of circular inserts 18 placed side by side basically corresponds to the length of the long axis of the tube cross-section, and in turn the tube is reinforced over the entire width (which is identifiable from left to right in FIG. 8). According to FIGS. 8 to 10, the tube may further have inner ribs 30 to the inserts 18 further provided at its end.

The insert in FIG. 9 is changed in a manner that has a plurality of S-shaped or Z-shaped bending portion compared to the insert of FIG. 4, resulting in a plurality of webs 20, the regions between which abut on their upper surfaces or lower surfaces in plane, respectively. The forms abutting on the lower surfaces correspond to the regions between the first web and the second web, between the third web and the fourth web, and between the fifth web and the sixth web, in the direction from left to right in FIG. 9. Correspondingly, the left region of the first web, the region between the second web and third web, the region between the fourth web and the fifth web, and the right region of the sixth web abut on the upper surfaces.

In addition, the reinforcing measure in FIGS. 9 and 10 is illustrated to the effect that the upper or lower boundary section of the tube is bent upward or downward in such a manner that the wall section 32 in the form of the web of the tube, which basically extends perpendicular to the tube axis in this case, is produced, for example, by the injection molded parts mentioned in the introduction section. This measure also provides the desired reinforcement of the tube end in certain applications that do not include any insert 18.

According to FIG. 10, this measure including any insert is combined similar to the insert of FIG. 2, for example, which is formed by extrusion molding and has a plurality of webs 20. The webs are formed integrally with the upper or lower boundary of the insert in series, while according to FIG. 9 (and FIGS. 3 and 4) they were first formed by the appropriate bending of the flat starting material of the insert.

INDUSTRIAL APPLICABILITY

The present disclosure relates to a heat exchanger and a method of manufacturing and assembling the same, and more particularly, the heat exchanger according to the present disclosure is associated with an air flow heat exchanger that is assembled by mechanical assembly (MA) as well as controlled atmospheric brazing (CAB). 

1. A heat exchanger, comprising at least one collector and at least one tube, in which the tube is installed in the collector by at least one seal disposed between the collector and the tube in such a manner that fluid connection is possible between the collector and the tube, wherein the tube comprises at least one reinforcing element that is provided only in a connection region between the tube and the collector.
 2. The heat exchanger according to claim 1, wherein the at least one tube is flat and has a relatively long axis, when viewed in cross-section, the length of which is 12 mm or more and/or up to 100 mm.
 3. The heat exchanger according to claim 2, wherein the at least one reinforcing element is basically an inner rib extending perpendicular to the long axis and/or basically a tube wall extending perpendicular to a tube axis.
 4. The heat exchanger according to claim 1, wherein the at least one reinforcing element is an insert.
 5. The heat exchanger according to claim 4, wherein the at least one insert has at least one step and/or at least one web and/or a circular or elliptical cross-section.
 6. The heat exchanger according to claim 1, wherein the at least one reinforcing element is a collar provided on a tube end.
 7. The heat exchanger according to claim 1, wherein the at least one reinforcing element is soldered to the tube.
 8. A method of manufacturing a heat exchanger by installing at least one tube in at least one collector by means of a seal disposed between the collector and the tube in such a manner that fluid connection is possible between the collector and the tube, wherein at least one reinforcing element is provided in or to the at least one tube.
 9. The method according to claim 8, wherein at least one inner rib is formed integrally (= in a manner that is built in) with the tube.
 10. The method according to claim 8, wherein the tube has a flat cross-section with a relatively long axis and a relatively short axis when viewed in cross-section and at least one wall of the tube is basically bent in a manner extending perpendicular to the tube axis.
 11. The method according to claim 8, wherein the at least one reinforcing element is soldered to the at least one tube.
 12. The method according to claim 11, wherein the at least one reinforcing element is soldered to the tube either before or after the tube is installed in the collector or together during installation of the tube.
 13. The method according to claim 8, wherein the at least one reinforcing element is formed by extrusion molding and/or bending. 